Disc drives are data storage devices that store digital data in magnetic form on a rotating storage medium called a disc. Each surface of a disc is divided into several thousand tracks that form tightly-packed concentric circles. Each track is further broken down into sectors.
Typically, disc drives contain unusable sectors when they are manufactured. These unusable sectors are called defective sectors. When defective sectors are discovered, each of the memory locations corresponding to the defective sectors are mapped to a good sector in another part of the data storage area of the disc. For this mapping purpose, spare sectors are reserved in a disc drive as substitutes for later detected defective sectors.
When a track with an unacceptable number of defects is found, rather than mapping individual sectors to spare sectors, the track is removed from a usable list of good tracks. These unusable tracks are called defective tracks. When a defective track is discovered, the memory locations corresponding to the defective track are mapped to a good track in another part of the data storage area of the disc. For this mapping purpose, spare tracks are reserved in a disc drive as substitutes for later detected defective tracks.
If there is an unacceptable number of defective tracks, the disc drive will fail because there are not enough adequate spare tracks that can be mapped. In addition, there is a yield loss of data storage capacity due to defective tracks. Thus, there is a need for a system and method for managing defective tracks.